The taxiing of aircraft between a parking position and a take-off and landing runway is usually realized with a tow tractor and/or with the thrust of the main engines of the aircraft. The tow tractor is required, in particular, for backing the aircraft (“Push-Back”) out of its parking position (“Nose In”). The taxiing to the take-off position and from the landing point to the parking position is realized with the main engines at low thrust. In alternative procedures, the aircraft is towed to a position near the take-off position with a tow tractor such that the main engines of the aircraft can be started at the latest possible time.
As an alternative, WO 2006/138267 A2 proposes to selectively drive the landing gear of the aircraft in the forward and reverse mode by means of an electric motor. In this case, the power supply of the motor is realized with the auxiliary power unit (APU).
In the standard procedure for taxiing aircraft to a take-off and landing runway, a relatively large quantity of fuel is consumed because the main engines need to generate the thrust required for taxiing and the efficiency of the main engines is relatively poor at low power. This is also associated with significant CO2 emissions. The airport personnel and neighboring residents are affected by the significant exhaust gas emissions, particularly by hydrocarbons and carbon monoxide. In addition, persons, vehicles and other aircraft are endangered by the jet blast of the main engines (“Jet Blast”). The noise generated by the main engines also represents a burden. The engine maintenance costs are increased due to the prolonged running time. Furthermore, tow tractors need to be made available for taxiing the aircraft out of the parking position such that the operating expenses are increased.
In the alternative procedure for taxiing the aircraft, the tow tractors are used much longer such that more tow tractors need to be available at an airport. In an aircraft with full fuel tanks, the attainable towing speed is also relatively slow such that backups may occur in the taxiing traffic. Furthermore, the power supply and air supply of the aircraft need to be ensured in order to operate, in particular, the air-conditioning system. This supply could be realized, for example, with the tow tractors, but this would reduce the towing capacity. The supply could selectively also be realized with the APU, but this would result in significant noise and exhaust gas emissions. In addition, the use of an APU is restricted or even prohibited in many airports. Furthermore, the APU operating time directly increases the APU maintenance costs.